The present invention relates generally to a dynamic behavior control apparatus for an automotive vehicle, and more specifically, to a method and apparatus for determining whether a wheel of an automotive vehicle has lifted from the pavement.
Dynamic control systems for automotive vehicles have recently begun to be offered on various products. Dynamic control systems typically control the yaw of the vehicle by controlling the braking effort at various wheels of the vehicle. By regulating the amount of braking at each corner of the vehicle, the desired direction of the vehicle may be maintained.
Typically, the dynamic control systems do not address roll of the vehicle. For high profile vehicles in particular, it would be desirable to control the rollover characteristics of the vehicle to maintain the vehicle position with respect to the road. That is, it is desirable to maintain contact of each of the four tires of the vehicle on the road.
Vehicle rollover and tilt control (or body roll) are distinguishable dynamic characteristics. Tilt control maintains the body on a plane or nearly on a plane parallel to the road surface. Rollover control is used to maintain the vehicle wheels on the road surface.
Such systems typically use position sensors to measure the relative distance between the vehicle body and the vehicle suspension. One drawback to such systems is that the distance from the body to the road must be inferred. Another drawback is that additional sensors must be used in addition to the sensors used in a rollover prevention system. This, of course increases the cost of the system.
It would therefore be desirable to provide a rollover detection system having reduced costs and increased reliability in predicting the occurrence of a rollover.
It is therefore one object of the invention to provide a rollover detection system that may be used in conjunction with the dynamic stability control system of the vehicle to determine rollover.
In one aspect of the invention, a system and method for detecting wheel lift of an automotive vehicle includes a yaw rate sensor that generates a yaw rate signal, a lateral acceleration sensor that generates a lateral acceleration signal, a roll rate sensor generating a roll rate signal, and a longitudinal acceleration sensor for generating a longitudinal acceleration signal. A controller is coupled to the yaw rate sensor, the lateral acceleration sensor, the roll rate sensor, and the longitudinal acceleration sensor. The controller determines a dynamic load transfer acting on the plurality of wheels as a function of yaw rate, lateral acceleration roll rate, and longitudinal acceleration. Normal forces for each of the plurality of wheels is determined as a function of the dynamic load transfer. Wheel lift is indicated when at least one of the normal forces for each of the plurality of wheels is less than a normal force threshold.
In a further aspect of the invention, a method for determining wheel lift of a vehicle comprises the steps of:
measuring a yaw rate;
measuring a lateral acceleration;
measuring a roll rate;
measuring longitudinal acceleration; and
determining wheel lift as a function of yaw rate, lateral acceleration, roll rate and longitudinal acceleration.
One advantage of the invention is that in vehicles employing a dynamic stability control system, additional sensors may not be required.
Other advantages and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.